Method for determining concentration; a dialyser

Abstract

A method for determining the concentration of an ion, atom or molecule bound in a complex. A reliable determination of the concentration of the ion, atom or molecule to be determined is possible in accordance with the invention in that the complexing of the ion, atom or molecule is prevented at least during the determination of the concentration by the addition or withdrawal of a substance. Also contemplated is a dialyser having a haemo-dialyser and/or a haemo-filter and an extra-corporal blood circulation with which a device for the adding of citrate to the blood is connected upstream and a device for the adding of a substitution solution containing ions to the blood is connected downstream of the haemo-dialyser and/or of the haemo-filter. Ion concentration in the dialysate downstream of the haemo-dialyser and/or of the haemo-filter is detected with respect to the direction of flow of the dialysate.

1. A method for determining ion concentration of blood of a patient in citrate anti-coagulated haemo-dialysis and/or haemo-filtration using a dialysate, comprising the steps of:
 adding citrate to the blood circulation during citrate anti-coagulated haemo-dialysis and/or haemo-filtration;  
 temporarily interrupting the adding of citrate to the blood circulation to prevent complexing of a relevant ion with the citrate before measuring a concentration of said ion in the dialysate;  
 measuring the concentration of said ion in the dialysate; and  
 determining the ion concentration of the blood on the basis of said measurement of the ion concentration in the dialysate.  
 
   
   
     2. The method in accordance with  claim 1 , wherein the measurement of the ion concentration in the dialysate is carried out after interrupting the citrate addition at the end of a length of time which is composed of a dead time caused by dead volumes and of a period of time required to reach a quasi-stationary state. 
   
   
     3. The method in accordance with  claim 1 , wherein the measurement of the ion concentration in the dialysate is carried out multiple times after interrupting the citrate addition and a measured value of said ion concentration is determined after reaching a quasi-stationary state. 
   
   
     4. The method in accordance with  claim 1 , wherein the measurement of the ion concentration is repeated multiple times after interrupting the citrate addition and a measured value of said ion concentration is determined by extrapolation of the ion concentrations obtained in the dialysate. 
   
   
     5. The method in accordance with  claim 1 , wherein the citrate concentration is interrupted for a pre-determined time interval and a measured value of said ion concentration is determined by integration of an area of a response function defined by the ion concentration in the dialysate as a function of time. 
   
   
     6. The method in accordance with  claim 1 , wherein the dialysate flow is reduced for the purpose of approximating the ion concentration of the dialysate to the ion concentration of the blood. 
   
   
     7. The method in accordance with  claim 1 , wherein the determination of the ion concentration of the blood takes place by calculation without reducing the dialysate flow. 
   
   
     8. The method in accordance with  claim 1 , wherein the detection of the ion concentration in the dialysate takes place by means of an ion-sensitive sensor in the dialysate flowing away from the dialyser. 
   
   
     9. The method in accordance with  claim 1 , wherein the determined ion concentration of the blood of a patient serves as a controlled variable whose value is influenced by control variables of citrate addition and/or addition of a substitution medium containing ions. 
   
   
     10. The method in accordance with  claim 1 , wherein an alarm is triggered when the determined ion concentration in the blood of the patient lies outside a permitted range or differs from a permitted value. 
   
   
     11. The method in accordance with  claim 1 , wherein the ion concentration in a compartment of the dialyser on the blood side thereof is determined without interrupting the citrate supply and is compared with a permitted threshold value of the ion concentration, with citrate feed being changed in dependence on this comparison. 
   
   
     12. The method in accordance with  claim 1 , wherein the ion includes calcium ions. 
   
   
     13. The method in accordance with  claim 1 , wherein the ion includes magnesium ions. 
   
   
     14. The method in accordance with  claim 1 , wherein the ion includes magnesium ions and calcium ions. 
   
   
     15. A method for determining ion concentration of blood of a patient in citrate anti-coagulated haemo-dialysis and/or haemo-filtration using a dialysate, comprising the steps of:
 adding citrate to the blood circulation during a citrate anti-coagulated haemo-dialysis and/or haemo-filtration process, said citrate forming a complex with an ion;  
 lowering a pH of said dialysate to release said ion from said citrate complex before determining a concentration of said ion in the dialysate; and  
 determining the ion concentration of the blood on the basis of the determination of the ion concentration in the dialysate.  
 
   
   
     16. The method in accordance with  claim 15 , wherein the pH is set to a range of pH=2-3. 
   
   
     17. The method in accordance with  claim 15 , wherein the setting of the pH in the dialysate takes place by means of an infusion of acid.